This invention generally relates to brake systems and more particularly relates to an electromechanical brake system and to a method for controlling an electromechanical brake system.
The more recent developments of current brake technology are directed towards research work on electric brake systems. Today""s hydraulic cylinders which apply the brake linings to the brake disc are replaced on each disc by a high-capacity electric motor. The electric brake does not need any mechanical or hydraulic parts such as vacuum brake boosters or tandem master cylinders. Further, the electric brake can take over the brake""s functions of today as well as functions of the future such as anti-lock brake system (ABS), traction slip control (TSC), electronic stability program (ESP) as well as the automatic brake management as it may, e.g., be provided with collision avoidance systems.
One example of such a system is disclosed in WO 95/13946. This so-called electronic brake system includes a central module and brake modules associated with the brake circuits or wheel groups. The central module of this disclosure may perform ABS and TSC computations, can adjust the braking force distribution and determine wheel-specific nominal braking pressure values.
It is an object of this invention to provide an electromechanical brake system and a method for controlling an electromechanical brake system, in particular for automotive vehicles, which features a safe and, simultaneously, low-cost design and only requires a minor installation effort, as well.
According to this invention, an electromechanical brake system is provided, in particular for automotive vehicles, which includes a pedal module for redundant detection of a drivers brake pedal actuation by means of a suitable sensor system. Further, the brake system may include a device for determining a nominal braking value on the basis of the driver""s intention and a brake module for actuating at least one wheel brake on the basis of the nominal braking value. Further, there is preferably a data transfer unit which is provided redundantly and which establishes a data flow connection between the pedal module, the device and the brake module, the device preferably including an error detection circuit which can detect any errors in the determination of the nominal braking value.
The brake module may be a circular module, with in each case it being possible that a power electronics system for actuating two actuators is contained in the circular module. Actuator-specific functional software (such as clamping force control) for two actuators may be implemented in each of the circular modules.
The modules may be connected by way of a double data bus or rather by way of the data transfer unit. The architecture of the brake system essentially is characterized by the signal and redundancy interfaces of the modules which, e.g., are error-tolerant, fail-silent or failsafe. Thus, the architecture sets special store by the allocation of the function of error detection by means of the modules themselves.
For cost-saving purposes, it is further possible to realize a central module function in a circular module or rather in a brake module.
Thus, in accordance with this invention, it is possible to achieve a modular structure, with errors being isolated on the component level so that error propagation is impossible. Further, by providing the data bus which directly connects the individual modules it is further possible to minimize the distance of transfer of analog signals so that the expenditure for EMC disturbance immunity can be kept relatively small.
A further advantage of this invention lies in the fact that, irrespective of the existence or non-existence of a braking intention, a clamping of a brake which is critical in terms of safety and is caused by an error in a computer, power electronics system or actuator with sensors is rendered impossible.